Ok well you could hire someone to do the art like oh I dunno maybe...Alex Grey or Chet Zar. Tool already hires outside help so obviously that can be replaced. I love Adam's art work and it clearly adds a lot to the band but that it's not irreplacable.

In my post I didn't mention many of the reasons why I think the band would choose to dissolve if the lineup had to change and you guys hit on part of it. By the way those riffs and effects are part of what I meant by atmosphere so I didn't exactly ignore them. Adam and Justin are replaceable as far as their playing abilities but the writing stage is definitely a big problem. They both write incredible riffs, etc...and the band would be hard pressed to replace them when it came time to write new material and still sound like Tool. It's happened to many bands before on the new album after replacing a key member, and the album flops. The lack of cohesiveness in writing is one reason why I don't think the band would continue.